[UWP] Propagate CollectionView BindingContext to EmptyView (#10574) fixes #9833

* Added repro sample

* Updated repro sample

* Updated EmptyView logic in UWP to propagate the BC

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue9833.cs

@@ -0,0 +1,103 @@
+using System.Collections.ObjectModel;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 9833, "[Bug] [UWP] Propagate CollectionView BindingContext to EmptyView",
+		PlatformAffected.UWP)]
+#if UITEST
+	[Category(UITestCategories.CollectionView)]
+#endif
+	public class Issue9833 : TestContentPage
+	{
+		readonly CollectionView _collectionView;
+		readonly Label _emptyLabel;
+
+		public Issue9833()
+		{
+			Title = "Issue 9833";
+
+			BindingContext = new Issue9833ViewModel();
+
+			var layout = new StackLayout
+			{
+				Padding = 0
+			};
+
+			var instructions = new Label
+			{
+				Text = "If the EmptyView BindingContext is not null, the test has passed.",
+				BackgroundColor = Color.Black,
+				TextColor = Color.White
+			};
+
+			_collectionView = new CollectionView();
+			_collectionView.SetBinding(ItemsView.ItemsSourceProperty, "Items");
+
+			var emptyView = new StackLayout
+			{
+				BackgroundColor = Color.LightGray
+			};
+
+			_emptyLabel = new Label
+			{
+				Text = "This is the EmptyView. "
+			};
+
+			emptyView.Children.Add(_emptyLabel);
+
+			_collectionView.EmptyView = emptyView;
+
+			layout.Children.Add(instructions);
+			layout.Children.Add(_collectionView);
+
+			Content = layout;
+		}
+
+		protected override void Init()
+		{
+
+		}
+
+		protected override void OnAppearing()
+		{
+			base.OnAppearing();
+
+			var emptyView = (View)_collectionView.EmptyView;
+			_emptyLabel.Text += $"BindingContext = {emptyView.BindingContext}";
+		}
+	}
+
+	[Preserve(AllMembers = true)]
+	public class Issue9833ViewModel : BindableObject
+	{
+		ObservableCollection<string> _items;
+
+		public Issue9833ViewModel()
+		{
+			LoadData();
+		}
+
+		public ObservableCollection<string> Items
+		{
+			get { return _items; }
+			set
+			{
+				_items = value;
+				OnPropertyChanged();
+			}
+		}
+
+		void LoadData()
+		{
+			Items = new ObservableCollection<string>();
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -196,6 +196,7 @@
       <SubType>Code</SubType>
       <DependentUpon>Issue9771.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Issue9833.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)RefreshViewTests.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue7338.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ScrollToGroup.cs" />

Xamarin.Forms.Platform.UAP/CollectionView/ItemsViewRenderer.cs

@@ -1,11 +1,10 @@
-using System.Collections.Specialized;
+using System;
+using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Threading.Tasks;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Data;
-using Windows.UI.Xaml.Controls.Primitives;
-using Windows.Foundation;
 using Xamarin.Forms.Internals;
 using UwpScrollBarVisibility = Windows.UI.Xaml.Controls.ScrollBarVisibility;
 using UWPApp = Windows.UI.Xaml.Application;
@@ -21,7 +20,8 @@ namespace Xamarin.Forms.Platform.UWP
 		UwpScrollBarVisibility? _defaultHorizontalScrollVisibility;
 		UwpScrollBarVisibility? _defaultVerticalScrollVisibility;
 		FrameworkElement _emptyView;
-		View _formsEmptyView;
+		View _formsEmptyView; 
+		bool _emptyViewDisplayed;
 		ScrollViewer _scrollViewer;
 		internal double _previousHorizontalOffset;
 		internal double _previousVerticalOffset;
@@ -388,7 +388,7 @@ namespace Xamarin.Forms.Platform.UWP
 			}
 
 			(ListViewBase as IEmptyView)?.SetEmptyView(_emptyView, _formsEmptyView);
-
+			
 			UpdateEmptyViewVisibility();
 		}
 
@@ -413,25 +413,46 @@ namespace Xamarin.Forms.Platform.UWP
 
 		FrameworkElement RealizeEmptyView(View view)
 		{
-			_formsEmptyView = view;
+			_formsEmptyView = view ?? throw new ArgumentNullException(nameof(view));
 			return view.GetOrCreateRenderer().ContainerElement;
 		}
 
 		protected virtual void UpdateEmptyViewVisibility()
 		{
-			if (_emptyView != null && ListViewBase is IEmptyView emptyView)
-			{
-				emptyView.EmptyViewVisibility = (CollectionViewSource?.View?.Count ?? 0) == 0
-					? Visibility.Visible
-					: Visibility.Collapsed;
+			bool isEmpty = (CollectionViewSource?.View?.Count ?? 0) == 0;
 
-				if (emptyView.EmptyViewVisibility == Visibility.Visible)
+			if (isEmpty)
+			{
+				if (_formsEmptyView != null)
 				{
-					if (ActualWidth >= 0 && ActualHeight >= 0)
-					{
-						_formsEmptyView?.Layout(new Rectangle(0, 0, ActualWidth, ActualHeight));
-					}
+					if (_emptyViewDisplayed)
+						ItemsView.RemoveLogicalChild(_formsEmptyView);
+
+					if (ItemsView.EmptyViewTemplate == null)
+						ItemsView.AddLogicalChild(_formsEmptyView);
 				}
+
+				if (_emptyView != null && ListViewBase is IEmptyView emptyView)
+				{
+					emptyView.EmptyViewVisibility = Visibility.Visible;
+
+					if (ActualWidth >= 0 && ActualHeight >= 0)
+						_formsEmptyView?.Layout(new Rectangle(0, 0, ActualWidth, ActualHeight));
+				}
+
+				_emptyViewDisplayed = true;
+			}
+			else
+			{
+				if (_emptyViewDisplayed)
+				{
+					if (_emptyView != null && ListViewBase is IEmptyView emptyView)
+						emptyView.EmptyViewVisibility = Visibility.Collapsed;
+
+					ItemsView.RemoveLogicalChild(_formsEmptyView);
+				}
+
+				_emptyViewDisplayed = false;
 			}
 		}